74 Anti-Theft Alarm Protector Switch - Part # 3951239 Question

[Victor S.]

Would this alarm switch (#3951239) have been factory installed on a 74 BB 4-speed?? I'm finding some of the original 74's had this switch, while others didn't - even though the 74 AIM lists this switch for ALL 74 models.

Trying to determine if this switch was originally on the 454 4 speed.
Thank you!

[Gary B.]

Re: 74 Anti-Theft Alarm Protector Switch - Part # 3951239 Question

Victor,




Gary

[Victor S.]

Re: 74 Anti-Theft Alarm Protector Switch - Part # 3951239 Question

Thank you for your response Gary - I looked in the judging guide before my post and the only thing the guide states is the position of the alarm lock on the outside drivers fender and how it operates using the key. Below is the pic of both the key lock (with terminals on the end) and the switch mounted on the inside of the fender of the lock (black part below, GM# 3951239). As stated in my original post - it appears some cars did not have this black switch and the alarm was only wired directly to the lock. I am trying to determine what configuration is correct for the 74 454 as mine was missing. 74 AIM shows switch listed for all cars but I do know of original cars that do not have the black switch shown. Thank you.

[Gary B.]

[John S.]

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[Gary B.]

Re: 74 Anti-Theft Alarm Protector Switch - Part # 3951239 Question

John,

The exact same switch is used at each headlight AND as an anti-tamper switch at the alarm. So, qty=3 per car.

Gary

[Jimmy P.]

Re: 74 Anti-Theft Alarm Protector Switch - Part # 3951239 Question

John, & Victor,
Yes, that black plastic safety switch is indeed used on the anti theft alarm for sure in 75- E77. It is the same part used for the headlights. I’m just not 100% sure it was used on all 74’s, unless it was something started later on. It’s mounted up against the key lock so that the end of the lock where the 90 degree bend is keeps the safety switch button pushed in. So, if someone tries to pull out the lock on the fender, it pulls away from the button and the alarm/warning sounds. Later on in ‘77 Corvettes there was a change in the system. The lock was removed from the front fender and moved (integrated with/to) the driver’s side door lock. Here’s a pic from the 75 AIM showing the set. I’m hoping a few of our 74 revision team members will check their cars to see if indeed the black plastic switch is present. I was going to contact them, but hopefully they will read this and respond.

PS….Vic, I would think that you would be able to see the female plug to the switch in your wiring harness nearby in that location if the car came with it?

Sorry, I see Gary beat me to the reply, John,, .

[John S.]

[Victor S.]

Re: 74 Anti-Theft Alarm Protector Switch - Part # 3951239 Question

Thanks all for the education on the switch. My original harness on my 74 BB does NOT have have the female plug for this switch. Also, after checking myself - I know of 2 other original 74 454's that did not have this switch - having only the ones for the headlights. That being said I know of a 74/350 that does utilize this switch as in the diagram Jimmy posted above. Looks like different applications depending on the model. Learn something new about these cars every day. Thanks again/V

[Jimmy P.]

[Doug C.]

Re: 74 Anti-Theft Alarm Protector Switch - Part # 3951239 Question

I'm the original owner of a 1974 with a build date of 10/5/73. It is an L48-350 and does not have the Alarm Protector Switch.

[Robert R.]

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[Keith K.]

Re: 74 Anti-Theft Alarm Protector Switch - Part # 3951239 Question

Vic - My '74 454 built June 24, 1974 does not have this switch

Keith